Bright and Bdp are two members of the ARID family of DNA binding proteins, and are known as eARIDs due to extended regions of homology. Bright has been shown to upregulate immunoglobulin heavy chain transcription by binding ATC motifs within matrix association regions (MARs). Bright has also been shown to play a role in cell cycle regulation. Bright expression is B cell specific, and is limited to two distinct developmental stages, the small pre-B II cell and the activated germinal center B cell. This limited expression pattern suggests that Bright may play an important role in these B cell stages. Bdp mRNA and protein expression are most abundant in B cell lines, as well as in spleen and testis, and Bdp binds with high affinity and specificity to the same MARs as Bright. This project will test the hypothesis that Bright is integral to B cell development and function, and that a lack of Bright will manifest a phenotype including decreased numbers of mature B cells, a lack of germinal centers, and an inability to respond to certain antigenic stimuli. This hypothesis will be tested by developing conventional and conditional Bright knockouts and determining the effects of this deletion on B cell development and function. The possibility of redudndant functions of Bright and Bdp will be tested by developing a Bdp knockout strain and breeding a Bright/Bdp double knockout.